[Not Applicable]
[Not Applicable]
Railway freight car trucks are usually configured in a three-piece arrangement consisting of a pair of laterally spaced sideframes, a bolster extending between the sideframes, and a pair of wheel sets located at opposite ends of the sideframes. Each sideframe includes a centrally located bolster opening for receiving the end of a bolster that extends laterally between and perpendicular to the sideframes. The ends of the sideframes are laterally aligned to receive an axle wheel set in what is usually termed the pedestal jaw of the sideframe. Examples of typical railway trucks are shown in U.S. Pat. Nos. 4,363,276; 4,838,174; 5,718,177; and 6,125,767.
A typical sideframe is comprised of an elongated top compression member that extends in a longitudinal direction parallel to the railway track. The sideframe also comprises two diagonally extending tension members that extend generally downwardly at an acute angle from near the ends of the top compression member. A bottom member extends longitudinally and joins the lower ends of the diagonal tension members. Column members extend generally vertically between the bottom member and the top compression member from a point near the junction of the diagonal tension members and the bottom member. Such column members form the bolster opening in the sideframe. A top portion or face of the bottom member of a sideframe is usually referred to as the spring seat of the sideframe, as it is adapted to receive the spring set upon which the ends of the bolster are supported. The bolster extends laterally between each sideframe with the ends of the bolster extending into the bolster openings where it is supported on spring sets. The spring seat includes upstanding structure, commonly referred to as spring retainers, for positioning and supporting the springs of the spring set. One example of a known spring retainer is shown in FIG. 2. Another example of a known spring retainer 2 is shown in FIGS. 3-5. As can be seen, the spring retainers 1, 2 generally comprise of upstanding flanges formed on the upper face of the spring seat 3, 4. As is shown in FIGS. 3 and 4, the spring seat 3 may also include depressions or recesses 5 for receiving the bottom faces of the springs. The arcuate broken lines 6 in FIG. 3 generally represent the springs from the spring set.
In order to reduce the overall weight of the railway truck, many of the components, such as the sideframes, are formed as hollow metal castings. Examples of processes for casting such components can be found in U.S. Pat. Nos. 5,481,986 and No. 5,752,564. As is described in the ""564 patent, such castings are created using molds consisting of sand cores supported between cope and drag mold portions. The cope and drag portions of the mold define a mold cavity. The sand cores are supported within the mold cavity and used to form the hollows and open spaces in the castings.
The sand cores are made in a core box consisting of cope and drag portions. The core box is filled, e.g., by a blower, with a mixture of sand and binder. The mixture is then cured to harden the resulting sand core sufficiently to allow it to be used for molding the cast component, e.g. the sideframe. As will be appreciated, the resulting cores have a negative image of the casting.
Problems can arise during the manufacture of the sand cores that are used to form these prior spring seats and spring retainers. Specifically, as can be seen in FIGS. 2-5, the prior spring retainers 1, 2 present abrupt, vertical surfaces that are generally perpendicular to the sand flow during creation of the sand cores. These vertical faces cause the sand to swirl as it is blown into the mold, thereby creating voids in the sand core and corresponding defects in the cast metal component.
The present invention addresses various aspects of these problems in the prior art.
Certain aspects of an embodiment of the present invention relate to an improved cast metal sideframe for use in a railway car truck. The sideframe has a spring seat for supporting springs from a spring set. The sideframe is molded using a core that includes a portion for defining the exterior surface of the spring seat. The spring seat includes a plurality of aerodynamically-shaped spring retainers formed on the spring seat. The aerodynamic shape of the spring retainers reduces the tendency for voids to form in the sand cores that are used to cast the sideframe.
The spring retainer may have a concave top face, which reduces the volume of material comprising the spring retainer. Reducing material volume is beneficial for reducing shrinkage during cooling of the sideframe, thereby reducing the tendency for separation, tears and cracks to form on the top surface of the spring retainer.
The aerodynamic shape may include forming portions of the retainer""s side wall at an obtuse angle with the top face of the spring seat. In one embodiment, the spring seat has an outer end, an inner end and a top face. The spring retainer may include a first face facing the outer end of the spring seat and a second face facing the inner end of the spring seat. The first and second faces of the spring retainer preferably form obtuse angles with respect to the top face of the spring seat. The first and second faces are generally transverse to the direction that sand flows during formation of the sand cores that are used to mold the sideframe. As a result, the tendency for sand to swirl and create voids during formation of the sand cores is reduced.
The spring retainers may include arcuate side walls for engaging and supporting springs from the spring set. Arcuate recesses may be formed in the top face of the spring seat, adjacent the arcuate side walls, for receiving the bottom faces of the springs.
Another aspect of the present invention relates to a method of making hollow cast metal sideframes of the type having a spring seat for supporting springs from a spring set. The method comprises the steps of providing a core to define the hollow interior of the sideframe, providing a mold with cope and drag portions and cop and drag mold surfaces defining a mold cavity, placing the core in the mold cavity, pouring molten metal into the mold to form a sideframe casting, removing the casting from the mold, and separating the casting from the core. The core comprises a spring seat portion for defining the exterior surface of the spring seat such that the exterior surface of the spring seat includes a plurality of aerodynamically-shaped spring retainers formed on the spring seat, whereby the aerodynamic shape of the spring retainers reduces the tendency for voids to form in the spring seat portion of the core.
Another aspect of the present invention relates to a method of making hollow cast metal sideframes of the type having a spring seat for supporting springs from a spring set. The spring seat has an outer end, an inner end and a top face. The method comprises the steps of providing a core to define the hollow interior of the sideframe, providing a mold with cope and drag portions and cop and drag mold surfaces defining a mold cavity, placing the core in the mold cavity, pouring molten metal into the mold to form a sideframe casting, removing the casting from the mold, and separating the casting from the core. The core comprises a spring seat portion for defining the exterior surface of the spring seat such that the exterior surface of the spring seat includes a plurality of aerodynamically-shaped spring retainers formed on the spring seat, wherein each aerodynamically-shaped spring retainer has a respective first face facing the outer end of the spring seat and a respective second face facing the inner end of the spring seat, and wherein the first and second faces form obtuse angles with respect to the top face of the spring seat, whereby the aerodynamic shape of the spring retainers reduces the tendency for voids to occur in the spring seat portion of the core.
Another aspect of the present invention relates to a method of making hollow cast metal sideframes of the type having a spring seat for supporting a holding a spring set. The method comprises the steps of providing a core to define the hollow interior of the sideframe, providing a mold with cope and drage portions and cop and drag mold surfaces defining a mold cavity, placing the core in the mold cavity, pouring molten metal into the mold to form a sideframe casting, removing the casting from the mold, and separating the casting from the core, the improvement wherein the core comprises: a spring seat portion for defining the exterior surface of the spring seat such that the exterior surface of the spring seat includes a plurality of spring retainers formed on the spring seat, at least some of the spring retainers having concave top faces, whereby the volume of material comprising the retainer is reduced.
Another aspect of the present invention relates to an improved cast metal sideframe of the type having a spring seat for supporting springs from a spring set. The spring seat comprises a plurality of spring retainers formed on a top face of the spring seat. At least some of the spring retainers having concave top faces, whereby the volume of material comprising the retainer is reduced.